The present invention relates to chaotic neural networks, and more particularly, to a non-linear circuit and a chaotic neuron circuit using the same.
Chaos phenomenon exists throughout every field of science: astronomical physics, biology, chemistry, engineering, physical geography, mathematics, medical science, meteorology, sociology, etc. and much research has been reported. Particularly, research into the cerebral nerve system has been actively proceeded with biochaos theory. Recently, the research and development has proceeded into a neuro-computer for artificially realizing the excellent information processing capacity of the human brain by applying the brain construction of a neural network and an information processing mechanism of the brain. However, it is criticized that the conventional neuron model is overly simplified from the real neuron. One characteristic of a real neuron which cannot be described by the conventional simple neuron model is chaos response. A chaotic neural network slightly modified from the neuron models of Caianiello and Nagumo-Sato has been suggested which realizes the network via hardware means.
FIG. 1 is a block diagram of a conventional linear chaotic neuron circuit.
In FIG. 1, the linear chaotic neuron circuit comprises resistors R4 and R6 each of which receives an input signal Xn at one end, a resistor R5 one end of which is connected to the other end of resistor R4, a resistor R7 connected between the other end of resistor R6 and ground, a diode D1 whose cathode is connected to the other end of resistor R4, a diode D2 whose anode is connected to the other end of resistor R4, a variable resistor R1 connected between a voltage V.sub.1 and the anode of diode D1, a variable resistor R2 connected between the cathode of diode D2 and a voltage V.sub.2, an amplifier 1 whose inverting input is connected to the other end of resistor R5 and whose non-inverting input is connected to resistor R7, and a variable resistor R3 connected between the output and inverting input of amplifier 1.
FIG. 2 is a graph showing the relation of an output voltage f(Xn) to an input voltage Xn of the non-linear chaotic neuron circuit shown in FIG. 1. Here, folding point values E1 and E2 are defined as 4(V.sub.1 -V.sub.D1)/3 and 4(V.sub.1 -V.sub.D1)/3, respectively.
The variables K1, K2 and K3 of FIG. 2 are determined according to the resistance values of the circuit shown in FIG. 1 and, assuming that resistors R4, R5, R6 and R7 each have the same value (R), can be expressed as follows. ##EQU1##
However, the constitution of the above non-linear chaotic neuron circuit having a non-linear characteristic as shown in FIG. 2 is complicated.